The endoplasmic reticulum (ER) and mitochondria are the primary compartments that regulate cellular metabolism. Compelling evidence suggests that these two organelles closely interact and coordinate to maintain the cell's metabolic integrity. Accordingly, disturbed ER homeostasis (or ER stress) and mitochondrial dysfunction often co-exist in pathological conditions such as neurodegenerative diseases and diabetes. In diabetic retinopathy (DR), hyperglycemia is sufficient to induce ER stress and oxidative stress, both contributing to retinal inflammation, vascular leakage, apoptosis, and ultimate neovascularization and neuronal degeneration. Intriguingly, additional to functional interactions, the ER and mitochondria are physically and biochemically interconnect through a highly specialized subdomain of the ER named the mitochondria- associated ER membrane (MAM). Although the exact mechanism of action of MAM remains obscure, emerging evidence suggests that MAM is a critical site for lipid and protein metabolism and calcium signaling. Several studies show that defective MAM function and/or structure negatively affects mitochondrial ATP production, increases ROS generation, exacerbates ER stress and leads to apoptosis. However, the role of MAM in healthy and diseased retina and retinal cells has not been studied. The overall goal of this pilot study is to establish a role of MAM in retinal cell metabolism in diabetes. In Aim 1, we will use innovative approaches to characterize the structural and biochemical changes in MAM in retinal cells exposed to diabetic insults and in the retina from diabetic animals. We will determine the functional consequence of MAM alterations on oxidative stress, ER stress, inflammation, vascular injury, and retinal cell death in DR. In Aim 2, we will use a specifically refined state-of-the-art proteomic technology to analyze the protein profile of MAM from normal and diabetic retinas. This comprehensive and unbiased assay of MAM proteins will confirm the role of MAM in regulation of retinal metabolism and explore the functional implication of MAM in signaling pathways related to DR pathogenesis. We anticipate that this novel and exciting project will generate essential data for future mechanistic study on mitochondria-ER regulation, which may also fill in a gap in our understanding of diabetes- induced metabolic defects in retinal cells and identify new therapeutic targets for DR.